class Solution
{
public:
    vector<int> findDisappearedNumbers(vector<int> &nums)
    {
        unordered_set<int> s(nums.begin(), nums.end());
        vector<int> result;
        int n = nums.size();
        for (int i = 1; i <= n; ++i)
        {
            if (!s.count(i))
            {
                result.push_back(i);
            }
        }
        return result;
    }
};